Emissions of halocarbons (CFCs, HCFCs, halons, PFCs, and HFCs) and other halogenated
compounds (SF6) on a substance-by- substance basis are described in detail in
Fenhann (2000). A list of the substances covered, together with their GWPs and
lifetimes (as in IPCC SAR; Houghton, et al. 1996), is given in Table 5-7.

Table 5-7:GWPs and
atmospheric lifetimes of halocarbons and other halogenated compounds.

Importantly, future emissions of halocarbons and other halogenated compounds
strongly depend on the technologies involved in their production and use. New
uses for these substances may arise or new products or technologies may replace
current uses. It is assumed here that the current mix of products continues
to exist for the next 100 years to 2100, with some generic technological improvements
as described below. This assumption, however, means that emissions projections
for industrial gases discussed in this section carry a substantial uncertainty.

Halocarbons are carbon compounds that contain fluorine, chlorine, bromine,
and iodine. Halocarbons that contain chlorine (CFCs and HCFCs) and bromine (halons)
cause ozone depletion, and their emissions are controlled under the Montreal
Protocol and its Adjustment and Amendments. According to the 1987 Montreal Protocol
and its subsequent amendments, consumption (the balance of production plus imports
minus exports) of CFCs is largely banned in developed countries after January
1996 (and developing countries after 2010), although some countries have failed
to meet the deadline. Furthermore, HCFC consumption will be subjected to a gradual
phase-out, with cuts from the 1986 base-year values of 35%, 65%, and 90% in
2004, 2010, and 2015, respectively. Final HCFC consumption phase-out will occur
in 2020 (2040 for developing countries).

The six modeling teams participating in the SRES process did not develop their
own projections for emissions of ODS and their substitutes. Hence, a different
approach for the development of long-range estimates for halocarbons and other
halogenated compounds was adopted. First, for ODSs the external Montreal Protocol
A3 maximum production scenario was used as a direct input to all SRES scenarios
(WMO/UNEP, 1998), since most measures in this A3 scenario have been implemented
already or are well established and under way (and so no large scenario variation
is expected). For other gas species, a simple methodology to develop different
emission trajectories consistent with aggregate SRES scenario driving-force
assumptions (population, GDP, etc.) was developed. Also, the assumed future
control rates have been adopted to conform to the SRES storylines presented
in Chapter 4. The underlying literature, scenario methodology,
and data are documented in more detail in Fenhann (2000) and are summarized
in this section.

The resultant emissions of Montreal gases, HFCs, PFCs, and SF6 are summarized
in Table 5-8. The effect on climate of each of the substances listed in Table
5-9 varies greatly because of differences in both the atmospheric lifetime and
the radiative effect per molecule of each gas. A good measure of the net climate
effect of halocarbons and other halogenated compounds is provided by their radiative
forcing. Radiative forcing will be addressed in IPCC's Third Assessment Report,
but is not discussed in this report.

Emissions of individual groups of halocarbons and other halogenated compounds
in the four families of SRES scenarios are presented below.

5.4.3.1. Hydrofluorocarbons

HFCs are beginning to be produced as replacements for CFCs and HCFCs. Unlike
the CFCs and the HCFCs, HFCs do not convey chlorine to the stratosphere and
thus do not contribute to ozone depletion.

For the development of future HFC emissions, Fenhann (2000) used a procedure
based on the work by Kroeze (1995) that includes two steps:

"Virtual" future CFC emissions are first calculated assuming a situation
without the Montreal Protocol.

CFCs are substituted with HFCs according to substitution percentages adopted
from the literature (Table 5-9) and also the various degrees of emission reduction
potentials from better housekeeping measures and technological change.

Concerning the first step of the methodology used in Fenhann (2000), 1990 CFC
emissions were taken from the Scientific Assessment of the Ozone Depletion (WMO/UNEP,
1998). Pre-Montreal 1986 emissions were obtained from McCulloch et al. (1994).
Future "virtual" (assuming no Montreal protocol) emissions of CFCs were assumed
to be proportional to their consumption, for which GDP numbers in the four marker
scenarios were used as a driver (see Chapter 4). The saturation
level of per capita demands was assumed to be the same in all four SRES scenario
families.

The projection of CFC emissions in the absence of the Montreal Protocol shows
how emissions would change under conditions of unrestricted production. However,
with the Montreal Protocol in place, other chemical compounds will be used to
replace the Montreal gases. To compute the amount of CFCs replaced with these
other compounds, future CFC emissions with the Montreal Protocol in place (according
to the WMO/UNEP A3 ODS scenario) were first subtracted from the "virtual" CFC
emissions.

Different assumptions about CFC applications as well as substitute candidates
were developed (Fenhann, 2000). These were initially based on Kroeze and Reijnders
(1992) and Midgley and McCulloch (1999), and subsequently updated using the
latest information from the Joint IPCC/TEAP Expert Meeting on Options for
the Limitation of Emissions of HFCs and PFCs (WMO/UNEP, 1999).

An important assumption (based on the latest information from the industry)
used in the current analysis is that relatively few Montreal gases will be replaced
completely by HFCs. Currently, HFC-134a is favored, and it is the only HFC with
sufficiently large sales to be included in the current production and sales
statistics (AFEAS, 1998). The global emissions of this gas are estimated to
be 0.1 kt HFC-134a in 1990 and 42.7 kt HFC-134a in 1997. Current data indicate
that substitution rates of CFCs by HFCs will be less than 50%. It was shown
recently that in the European Union the substitution rate of CFCs by HCFCs was
26%, and the HFC share was 6% or a total of 32% (McCulloch and Midgley, 1998).
Time series data for the global sales from AFEAS (1998) confirm a 763 kt per
year reduction in CFC production and use from the peak production year of 1987
through 1996. An increase in the total HFC and HCFC production and use was 340
kt per year, or a 44% substitution up to 1996. In Fenhann (2000) future technological
developments are assumed to result in about 25% of the CFCs ultimately being
substituted by HFCs (Table 5-9). This low percentage not only reflects the introduction
of non-HFC substitutes, but also the notion that smaller amounts of halocarbons
are used in many applications when changing to HFCs and that emissions are reduced
by increased containment and recycling. A general assumption is that the present
trend to not substitute CFCs with high GWP substances, including PFCs and SF6, will continue. The substitution rates shown in Table 5-9 were used in all
four scenarios; the technological options adopted are those known at present.
Further substitution away from HFCs is assumed to require a climate policy.

Hydrocarbons are expected to be the substitutes used in the aerosols/propellant
sector, except for situations in which the flammability of hydrocarbons would
be a problem and also in metered dose inhalers (to avoid possible adverse clinical
effects). HFC-227ea and HFC-134a, and possibly HFC-152a are expected to replace
hydrocarbons (Table 5-9; WMO/UNEP, 1999).

CFC-113 was used extensively as a cleaning solvent for metal, electronics,
and textiles. The general trend in this area now is toward water-based systems.
However, as suggested by Table 5-9 a small fraction (0.5%) of the CFC in this
sector is substituted by HFC-43-10 (Kroeze, 1995).

The WMO/UNEP (1998) report states that no fluorocarbons are now used for open
cell foams, an assumption also adopted in the scenarios.

It is expected that closed cell foams and refrigeration will
be the largest demand sectors for HFCs in the future. For closedcell
foams, the substitution is expected to be 50%, one-half as HFC-134a and the
other half as the liquid HFC-245fa (expected to be commercially available by
2002; Table 5-9) (Ashford, 1999). In some cases, HFC-365mfc will be used instead
of HFC-245fa. However, all the calculations in Table 5- 9 were carried out for
HFC245fa, since these two substances have almost the same climate effect.

Prior to 1986, the main refrigerants in use were CFCs, HCFCs, and ammonia.
In response to the Montreal Protocol, HFC and hydrocarbon refrigerants have
been promoted as the primary alternatives (WMO/UNEP, 1999). The main HFC assumed
to be used for stationary cooling is HFC-134a, with 5% of the demand substituted
by HFC-125 and another 5% by HFC-143a (Kroeze, 1995). This would agree with
the reported measurements of these two substances in the atmosphere. According
to Kroeze (1995) about 2% might be substituted by HFC-32.

Before 1993, all air-conditioned cars were equipped with systems using CFC-12
as a refrigerant. Over the lifetime of a car, 0.4 kg of this halocarbon was
emitted every year. In 1994, two years after the new refrigerant HFC-134a had
become available globally in sufficient quantities, almost all major vehicle
manufacturers began to use HFC-134a. This conversion was accompanied by a significant
reduction in annual losses of refrigerants per car, down to 0.096 kg of halocarbon
(Preisegger, 1999). Therefore the substitution rate in Table 5-9 for mobile
cooling is assumed to be 25%.

In the fixed fire extinguishers sector, only about 25% of the systems that
formerly used halons now use HFCs, mainly HFC-227ea. The rest use CO2 , inert
gas mixtures, water-based systems, foam, dry powder, etc. (WMO/UNEP, 1999).
Increased environmental awareness in the industry is assumed to have resulted
in the reduction of HFC emissions by a factor of three, compared to former practice.

For portable fire extinguishers the substitution rate is assumed to be only
1%, even less than the 2% assumed by Kroeze (1995).

CFCs have also been used for other purposes, such as sterilants, tobacco expansion,
and others. Kroeze (1995) assumes a 30% substitution by HFCs. However, in the
SRES scenarios this value is reduced to 10% to remain consistent with the above
assumption that HFCs ultimately will substitute for about 25% of the CFCs.

As well as using non-halocarbon substitutes, HFC emissions can be avoided by
better housekeeping, for instance by reduced spilling of cooling agents. Leakage
control equipment can also serve this purpose. Finally, halocarbons can be recovered
for recycling or destruction when equipment is discarded. Some of this emission
reduction potential is likely to be implemented as a result of technological
changes introduced to control ODSs. In the SRES scenarios, reduction rates were
varied over time and between industrialized and developing countries to reflect
the definitive features of the underlying storylines (Chapter
4). Generally, the reduction rates are assumed highest in scenarios that
emphasize sustainability and environmental policies (B1 family). These reductions,
however, were not associated with any explicit GHG reduction policies, as required
by the SRES Terms of Reference (see Appendix I).
In one scenario family, A2, no reductions were assumed, whereas in the A1 and
B2 families reduction rates were set at intermediate levels.

In addition to consumption-related emissions of HFCs, HFC-23 is emitted as
an undesired by-product from the HCFC-22 production process. As a result of
the Montreal Protocol, the direct use of HCFC-22, and hence the related HFC-23
emissions, will come to a halt in 2050. To calculate the HFC-23 emissions, information
from Oram et al. (1998) was used (estimated emissions of HFC-23 at 6.4 kt in
1990). By relating this value to 178.1 kt HCFC-22 emitted in 1990 (WMO/UNEP,
1999), an emissions factor of 0.036 tons of HFC-23 per ton of HCFC-22 was calculated
and applied to estimate future emissions. Since this estimation procedure does
not take into account any pollution control regulations (that are not driven
by climate considerations), it may result in an overestimation of HFC-23 during
the early decades of the 21 st century, until HCFC production is phased out
under the Montreal Protocol. After the phase-out of HCFC-22 consumption, some
HFC-23 emissions will still occur because of the continued HCFC-22 feedstock
production allowed under the Montreal Protocol. The resultant projections are
shown by individual HFC in Table 5-8.

In general, the SRES scenarios might underestimate HFC emissions if the substitution
of CFCs with alternatives that have no radiative forcing effect and with more
efficient HFCs-based technologies does not penetrate as quickly as is assumed,
especially in developing countries. However, more effective technologies and/or
suitable non-HFC alternatives may be developed, which would lead to even lower
emissions.